CHICAGO (Reuters) - A highly sensitive microchip may help
doctors detect rare traces of cancer circulating in the
bloodstream, offering a way to better manage treatment, U.S.
researchers said on Wednesday.

The device can isolate, count and analyze circulating tumor
cells from a blood sample, the team at Massachusetts General
Hospital and Harvard Medical School in Boston said.

These circulating tumor cells, or CTCs, are the tiniest
fragments of tumors, which are carried in the blood.

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Doctors have known about them for some time, but because
they are so rare and so fragile, they have been hard to trap
and study in a meaningful way.

"What our technology does is increase the sensitivity many,
many fold, to a point where it can become a tool that can be
used clinically," said Mehmet Toner, whose group developed the
device.

He said routine monitoring of these cells could help
doctors tailor treatments to patients and may one day aid with
diagnosis.

"Nine out 10 deaths in cancer are due to the metastatic
process because the cancer spreads to other parts of the body,"
said Toner, whose study appears in the journal Nature.

"These are really the cells that end up killing people."

Current blood tests to detect these rare cells involved
many steps of mixing and spinning and shaking, often killing
what few cells they found.

"We went to the blackboard and designed it from scratch,"
Toner said in a telephone interview.

TRAPPING CANCER CELLS

The device they made uses a business-card sized silicon
chip. It has microscopic posts that are coated with antibodies
that recognize cancer cells.

As blood flows over the chip, these posts act like glue,
trapping cancer cells and leaving blood cells behind.

Older methods may have produced one to five cells out of 60
billion cells screened in an 8-milliliter tube of blood. The
new device can find 1,000 cancer cells.

The researchers tested their chip against blood samples
from 68 patients with five types of tumors -- lung, prostate,
breast, pancreatic and colorectal.

Out of 116 samples, they found circulating tumor cells in
all but one sample, and none were found in samples taken from
healthy people.

And the test was sensitive enough to detect changes in
circulating tumor cell levels during treatment, with drops in
detected CTC levels matching tumor shrinkage seen on standard
CT scans.

"Suddenly, we have a great opportunity to have an impact in
cancer in major ways," Toner said.

He said the technology will allow for much more
personalized cancer care. "You get a sense of how a patient is
responding to treatment."

Eventually, it also may prove useful for cancer screening.
And ready access to live cancer cells will advance cancer
research.

"We will start to understand the biology of cancer much
better," Toner said.